PREHEAT oven to 350° F. Grease two 9-inch-round baking pans or one 13 x 9-inch baking pan.
FOR CAKE:COMBINE flour, cocoa, baking soda and salt in small bowl. Beat butter, granulated sugar, oil and vanilla extract in large mixer bowl on medium speed for 4 minutes. Add eggs; beat well. Gradually beat in flour mixture alternately with milk. Spread into prepared pan(s).
BAKE for 20 to 25 minutes or until wooden pick inserted in center comes out clean. Cool in pan(s) for 15 minutes; invert onto wire rack(s) to cool completely. Frost with Rich Chocolate Frosting.
FOR RICH CHOCOLATE FROSTING:
BEAT powdered sugar, cocoa, milk, butter, oil, vanilla extract and salt in small mixer bowl until smooth and creamy.